Is Oxygen Per Cent in Biogass High Enough to Make Compression Dangerous?

"Bio gas is approximately 60% methane and 40% co2 and traces of H2S.... First, you might want to get rid of H2S as it will be corrosive - running the gas through iron shavings should do the trick. ...An easy way to get rid of the CO2 is to run it through lime solution,,, but it is going to take energy to recycle the lime (or you can compress the bio gas to a high enough pressure and low enough temperature and at the point when CO2 liquifies, try to get rid of it). " At this point the biogas is equivalent to CNG...

why do you think oxygen may left over ??

I heard that biogass released from bacteries which lives in anaerobic places . and in the presence of oxygen they will not live .( im not so sure about this).

Methanogenesis is largely prevalent in reductive environments over against oxidizing. If you are thinking about an aqueous environment you are mostly correct, but it depends very much on the bacterial strain. Either way, the % of oxygen is likely to be very low unless it has been separatley entrained or the digester efficiency is poor.

Thank you JNB. I think you adequately addressed it. I have read various articles showing the composition of unscrubbed biogass and some list oxygen and some dont. This mystified me somewhat so you seem to be addressing it by directing attention the the particular strain of bacteria. Btw, thank you Solar Eagle. I actually know about the two types of scrubbing you mentioned. You can also use water soaked in fireplace ash which I am sure you would not need to reprocess since the stuff is so readily available. JNB, not sure what you meant about oxygen being "seperately entrained". Can you explain? Thank you.

Sorry dijeferidu- typing too fast. That reference was actually to air entrainment; basically any exterior source of air that may be drawn in after the digester. BTW- monoethanolamine (MEA) is commonly used to scrub both H2S & CO2. More expensive than fireplace ashes tho!

Thank you JNB. Interesting about monoethanolamine. Haven't come across that one yet. Btw, I dont know if you had seen my earlier post about siloxanes? I had found a strain of algae diatom that produces a large % of oil and found that it needs silicon to create its cell walls. I wondered if the biogass from landfills could possibly supply the silicon since it is often tainted with siloxanes. I mean something like percolating the unscrubbed gas through a bed of the algae. Or would there need to be an intermediate step to break down the siloxane and make the silicon accessible?

No I haven't- that's interesting, if you can point them out. Are you talking about the saltwater algae that has been researched as a source of biodiesel feedstock?

I would be cautious about percolating it, as that would be one way of allowing air contamination. It's still a great idea for utilizing the CO2 tho- perhaps countercurrent flow through a pressurized packed column (at a guess operated partly flooded so you don't carry out foam), top fed with cool RO water to strip the CO2 & then fed to the growth vats or just allow to flash off....... Lower pressure requirements than liquification & you can calculate saturation points from pressure & temp. I agree with Solar Eagle about that being the best way to remove it on a large scale tho unless you have a use for the byproducts. Same problem with iron filings- surface area gets used up & then it has to be replaced. i'd imagine that's why industry uses MEA & imine derivatives that can be constantly fed. Anyone else know?

Thank you. The particular strain I was reading about was Bacillariophyceae and it is a freshwater diatom.